Vehicle compartments, such as engine compartments, contain a variety of different reservoirs used to store various vehicle fluids. To reduce vehicle costs, some of those fluid reservoirs, especially in emerging markets, do not contain any kind of sensing device to indicate when a low fluid level has been reached (e.g. washer reservoirs or gasoline reservoirs in certain vehicle markets). Therefore, the customer does not know when to fill the reservoir unless the compartment cover (e.g., hood for engine compartments) is opened for inspection, or the functionality of the vehicle is compromised due to a lack of fluids.
A low fluid level in a reservoir can be particularly problematic in emerging markets where sensing devices are often not included to keep vehicle costs low. For example, flexible-fuel vehicles (FFV) or dual-fuel vehicles (colloquially called flex-fuel vehicles), prevalent in markets like Brazil, are alternative fuel vehicles that have an internal combustion engine designed to run on more than one fuel—usually gasoline blended with either ethanol or methanol fuel, and both fuels are stored in the same common tank. Modern flex-fuel engines are capable of burning any proportion of the resulting blend in the combustion chamber as fuel injection and spark timing are adjusted automatically according to the actual blend detected by a fuel composition sensor. Flex-fuel vehicles are distinguished from bi-fuel vehicles, where two fuels are stored in separate tanks and the engine runs on one fuel at a time, for example, compressed natural gas (CNG), liquefied petroleum gas (LPG), or hydrogen.
North American and European flex-fuel vehicles are generally optimized to run on E85, a blend of 85% anhydrous ethanol fuel with 15% gasoline. This upper limit in the ethanol content is set to reduce ethanol emissions at low temperatures and to avoid cold starting problems during cold weather, at temperatures lower than 11° C. (52° F.). The alcohol content is reduced during the winter in regions where temperatures fall below 0° C. (32° F.) to a winter blend of E70 in the United States. However, Brazilian flex fuel vehicles are optimized to run on any mix of E20-E25 gasoline and up to 100% hydrous ethanol fuel (E100) so the Brazilian flex vehicles are generally equipped with a small gasoline reservoir for cold starting the engine when temperatures drop below 15° C. (59° F.). In these markets, it's important to know when there is a low fluid level in the reservoirs; otherwise, the vehicle may not start in cold weather scenarios.
It would be advantageous to have the ability to monitor reservoir fluid levels in these emerging market vehicles without the use of additional sensors, which adds to the cost and complexity of the vehicle.